Nebulizers are medical devices that generate aerosol from a liquid using compressed gas or piezoelectric energy. Jet nebulizers pull liquid from a liquid reservoir and force the liquid, using compressed gas from a tank or air compressor, through a small restricted opening of a jet nozzle cover which causes nebulization. Ultrasonic nebulizers utilize a piezoelectric motor or piezo-oscillating element. Passing liquid through an aperture mesh or membrane that vibrates at ultrasonic frequencies causes nebulization. All nebulizers typically consist of a housing containing a liquid reservoir and a nebulization chamber with a nebulization generating means, e.g., jet nozzle or vibratable mesh, and an aerosol outlet port for receiving a mask or a mouthpiece, either directly or with a T-piece adapter. Some nebulizers are breath-enhanced and may contain ambient air inlets to more efficiently entrain and remove aerosol.
Nebulizers are drug delivery devices when they deliver aerosolized medications to a patient via a mouthpiece, nosepiece, or mask. Nebulizers are primarily used for delivering aerosolized medication, including bronchodilators, for relieving symptoms associated with asthma and chronic obstructive lung disease, COPD. Such asthma and COPD patients often have compromised lung function and trouble breathing. Jet nebulizers are primarily used in the hospital setting for treating these patients. A major drawback to most jet nebulizers, including those requiring a T-piece adapter, is that aerosol is wasted during patient exhalation and aerosol released in the hospital or emergency room can lead to occupational exposure. A large spacer device may be fitted to a nebulizer to help reduce occupational exposure. But a spacer can make delivery inefficient by reducing the concentration of the nebulized bolus, and the spacer does not entrain aerosol from within the nebulizer. A nebulizer can sometimes be fitted with an exhalation filter, which reduces occupational exposure, but does not prevent aerosol waste.
To reduce occupational exposure and aerosol waste during exhalation, a new class of jet nebulizers were developed that coordinated the generation of nebulized aerosols with the breathing cycle. The premise was that nebulization occurred only during inhalation, and not during exhalation. Such nebulizers formed a class known as breath-actuated jet nebulizers. Because these breath-actuated jet nebulizers were primarily intended for treating asthmatics and COPD patients of compromised lung function, and including pediatric patients and those utilizing a mask, they were purposely invented to have a very low triggering point so that normal breathing with no additional inhalation effort is required to actuate nebulization. Otherwise, actuation would be difficult or unattainable by these patients. These breath-actuated jet nebulizers have an actuator having biasing means with a predetermined spring or elastic force that is exceedingly weak. Thus, these prior art breath-actuated jet nebulizers have a very low, constant, single, threshold level of actuation. This threshold level of actuation is so low, that from the patient's perspective, may be considered negligible or insignificant if not associated with an increased inhalation effort that can be experienced. These breath-actuated jet nebulizers lack structures, mechanisms, and dialable interface components that would enable a patient user to increase the threshold level of actuation beyond a minimum baseline level. When and if actuation can be bypassed, there would be no threshold of actuation; breath coordinated actuation does not take place in a continuous nebulization mode.
By way of example, United States Patent Application Number 2007/0023036 to Grychowski et al. describes a breath-actuated nebulizer having a moveable gas diverter located at a variable height above the jet nozzle, which changes a deflection angle of gas emitted from the top of the gas nozzle across the liquid outlet. The gas diverter moves from a nebulizing position to a non-nebulizing position in response to a patient's breathing. Grychowski et al. teaches that a membrane provides an elastic triggering threshold that permits cyclical nebulization to occur that coincides with the breathing of the patient. This threshold is set to fall within normal human breathing parameters so that the diverter moves into and out of proximity with the nozzle top as a result of the patient's normal breathing . . . this level may be approximately less than or equal to 3.0 cm of water. There are no different negative pressure threshold settings of actuation and no dialable means of changing actuation of the device.
By way of another example, U.S. Pat. No. 7,131,439 to Blacker et al. describes a breath-actuated nebulizer having a nozzle cover that moves in response to a patient's breathing. This nozzle cover is associated with an actuator piston that responds to a negative pressure in the range of 0.5 to 1.0 cm of water because Blacker et al. teaches that it is desirable that a nebulizer have adequate sensitivity to quickly respond to an inhalation while not adversely restricting the patient's inhalation. Blacker et al. also teaches a relief piston separately mounted and independently movable with respect to the actuator piston may be used to alleviate inhalation effort after an initial period of inhalation. The relief piston is preferably configured to increase the amount of additional ambient air provided to the chamber as the patient's inhalation increases to keep the negative pressure from rising to a point that makes inhalation difficult for the patient. As such, the relief piston opens to prevent negative pressure from increasing above 1.0 cm of water. The relief piston also has the effect of reducing the resistance to inhalation. Actuation and movement of the actuator piston can be bypassed with a continuous nebulization selection lever, and when in this continuous operation mode, there is no threshold of actuation for nebulization to take place. There are no different negative pressure threshold settings of actuation. Actuation of the actuator piston can only be turned on or turned off, and the negative pressure of the device remains the same; negative pressure is sustained at the same 1.0 cm of water either way.
While these breath-actuated nebulizers serve their intended purpose, they, like regular jet nebulizers, are deficient in being able to increase negative pressure to a different level, and do not have increased negative pressure threshold settings of actuation. It can be appreciated that in certain circumstances, increased negative pressure thresholds and increased inhalation effort can be desirable, and in this sense, the present invention departs from the usual doctrines of effortless asthma and COPD aerosol treatments. For instance, higher negative pressure thresholds, thresholds above 3.0 cm of water, require an increased inhalation effort with greater exertion of the muscles involved in respiration. These higher negative pressure thresholds, as experienced by the patient, can exercise the respiratory muscles beyond what normal breathing can do. Such higher negative pressure thresholds can be used for strength training of the muscles involved in respiration, but can also be used to help maintain lung elasticity and improve respiratory health. Only a nebulizer of the present invention having these different negative pressure threshold settings could be used by chest surgery patients, instead of an incentive spirometer, to help remove secretions and prevent atelectasis on the day of their operation. The present invention may also serve as an incentive device because movement of the negative pressure threshold valve assembly from inhalation may provide a visual signal, and perhaps an auditory signal, to the user. Such a stand-alone nebulizer device has the potential to reduce overall hospital costs, while saving time and providing greater convenience. The prior art nebulizers of Grychowski et al. and Blacker et al. are not capable of providing negative pressure threshold resistance training because they have a negative pressure threshold that is exceedingly low and does not require an increased inhalation effort from the patient. Their nebulizers also cannot make inhalation more difficult than normal breathing, and therefore, lack the therapeutic benefits associated with an increased negative pressure threshold.
For patients with adequate lung function that can achieve greater inhalation effort, the different negative pressure threshold settings of this novel nebulizer can have profound effects on aerosol delivery dynamics. More specifically, by having actuation of nebulization and aerosol entrainment associated with different negative pressure threshold settings, the nebulizer can be used to selectively target aerosols to one or more different airway regions. In effect, aerosol actuation, entrainment, and delivery occur when one or more different airways are optimally expanded with the desired pressure for enhanced drug targeting and delivery efficiency.
More pharmaceuticals are being made available for inhalation. This includes pharmaceuticals that can be delivered to the systemic circulation via the pulmonary route. As an improved drug delivery device, the present invention can improve the delivery dynamics and targeting of these drugs. Selective targeting of aerosols to one or more different airway regions can aid in the targeting of aerosolized chemotherapies against lung cancer. Selective targeting of aerosols to one or more different airway regions can also have profound military medicine applications, including biodefense to counter bioterrorism, by coating upper airways with antibiotics against anthrax or other infectious agents, or by providing anticholinergic agents to the systemic circulation via alveoli as an antidote to nerve agent exposure. The present invention also has the potential to enhance the deliverability of drug candidates in development, which has the potential to reduce drug development costs.
Accordingly, there is a need for an improved nebulizer that can overcome one or more of the limitations discussed above, and open the way for new and improved methods of providing nebulization treatments.